Hub assembly for in-line centrifugal separator

ABSTRACT

The hub assembly comprises a cigar-shaped hub carrying vanes. The hub defines a central bore opening at the downstream end. Two or more vanes define conduits leading into the bore. The assembly is normally mounted in the inlet of a vortex tube. The vanes force the gas flow into helical paths for centrifugal separation of entrained liquid. The bore and conduits connect the low pressure zone at the axis of the vortex tube with the space exterior of the vortex tube.

United States Patent Willis [54] HUB ASSEMBLY FOR IN-LINE CENTRIFUGALSEPARATOR [72] Inventor: Robin Burke Willis, Edmonton, Al-

berta, Canada [73] Assignee: Ports-Test Manufacturing Ltd., Ed-

monton, Alberta, Canada 22 Filed: Aug. 24, 1970 211 Appl. No.: 66,468

[52] US. Cl. ..55/457, 55/340, 138/37, 138/39, 209/211, 210/512 [51]Int. Cl. ..B0ld 45/12 [58] Field of Search ..55/338, 339, 340, 347, 348,55/456, 457; 209/144, 211; 138/37, 39;

[56] References Cited UNITED STATES PATENTS 2,569,909 10/1951 Umney..55/347 2,918,139 12/1959 Silverman ..55/339 [151 3,693,329 51 Sept.26, 1972 3,254,478 6/1966 Szego ..55/340 3,360,909 1/1968 Barnevias..55/348 3,517,821 6/1970 Monson et a1. ..55/457 FOREIGN PATENTS ORAPPLICATIONS 1,146,262 3/ 1969 Great Britain ..55/57 PrimaryExaminer-Bernard Nozick Attorney-Ernest Peter Johnson 1 5 7 1 ABSTRACTThe hub assembly comprises a cigar-shaped hub carrying vanes. The hubdefines a central bore opening at the downstream end. Two or more vanesdefine conduits leading into the bore.

The assembly is normally mounted in the inlet of a vortex tube. Thevanes force the gas flow into helical paths for centrifugal separationof entrained liquid. The bore and conduits connect the low pressure zoneat the axis of the vortex tube with the space exterior of the vortextube.

7 Claims, 3 Drawing Figures HUB ASSEMBLY FOR IN-LINE CENTRIFUGALSEPARATOR BACKGROUND OF THE INVENTION This invention relates to a hubassembly for use in a centrifugal separator of the in-line recyclingtype.

Reference is made to co-pending U.S. Pat. application Ser. No. 66,545wherein an in-line recycling separator is described.

This type of separator has an outer shell which is open-ended andcylindrical in form. In use, the shell is tied into a flowline carryinga gas flow containing a small quantity of entrained liquid. Positionedwithin the shell is at least one vortex tube. Each vortex tube comprisestwo co-axial tubes spaced apart longitudinally to define acircumferential gap between them. The vortex tube and shell define anannular space between them which is suitably closed at its ends. Theinterior of the vortex tube and the exterior annular space communicatevia the circumferential gap. The inlet and outlet of the vortex tubecommunicate the inlet and outlet of the shell so that the pipeline flowpasses through the vortex tube.

A hub assembly is mounted within the inlet end of the vortex tube. Thishub assembly comprises a cigarshaped hub which is concentrically fixedwithin the vortex tube. An annular passage is defined between the huband the vortex tube wall. The hub carries a number of curved vanes whichprotrude into this passage. The hub also defines a longitudinal borewhich communicates the vortex tube interior at the hubs downstream end.The hub assembly includes a cross pipe connecting the upstream end ofthe bore with openings in the upstream end of the vortex tube wall.

The hub assembly has several functions, namely:

1. It causes acceleration of the pipeline flow by providing arestriction in the flow path.

2. Its vanes force the flow to follow helical paths around the innersurface of the vortex tube. This, of course, results in centrifugalseparation of the liquid from the gas. The liquid accumulates as a layeralong the vortex tube wall.

3. The conduit formed by the bore and cross pipe connects a low pressurezone, which exists along the longitudinal axis of the vortex tube, withthe annular space. As a result, the annular space is maintained at alower pressure than that which exists at the periphery of the interiorspace of the vortex tube. This results in suction being applied at thevortex tube gap the liquid and some gas are therefore sucked into theannular space. The liquid falls to the bottom of the annular space dueto gravity and the gas is recycled into the vortex tube via the conduit.

SUMMARY OF THE INVENTION The present invention is directed to animproved hub assembly. According to its key feature, the various partsof the assembly have been integrated into a single integral part whichcan be easily and cheaply cast or molded. This contrasts with previousassemblies whose parts had to be welded together.

Turning now to providing a broad description of the assembly, itincludes an elongate hub. This hub carries four vanes. The vanesprotrude outwardly from the hub at spaced intervals. They arelongitudinally curved so as to define with the hub four peripheral,curved grooves extending lengthwise along the hub. The hub defines abore along its longitudinal axis. This bore is open at its downstream orsecond end but does not quite extend all the way back to the hubsupstream or first end face. The bore is therefore closed at its upstreamend.

The assembly is generally cylindrical in form so as to fit snugglywithin a vortex tube. The longitudinal axis of the hub coincides withthe center of a circle drawn around and tangential to the outermostsurfaces of the vanes in a plane at a right angle tothe said axis. Whenthe assembly is mounted within a vortex tube, the bore communicates theinterior of the vortex tube at its longitudinal axis. The bore thereforeopens into the low pressure zone which exists within the gas vortexdisposed along this axis when the separator is in operation.

One pair of oppositely disposed vanes is thicker at their upstream orfirst ends than the other pair of vanes; a sealed passageway connectingthe upstream end of the hub bore with an opening in the vanes outermostsurface is formed or defined by each of the thick vanes. When theassembly is welded into place in a vortex tube, the passageway openingregisters with an opening in the vortex tube wall. As a result, the boreand passageway provide a sealed conduit connecting the annular spaceabout the vortex tube with the low pressure zone within it.

By having vanes which are an integral part of the hub assembly anddirecting the passageway through one of the vanes, an assembly isprovided which can be formed, as by casting, into one integral unit orpart.

DESCRIPTION OF THE DRAWINGS In drawings which illustrate an embodimentof the invention:

FIG. I is a perspective view of the hub assembly;

FIG. 2 is a view similar to that of FIG. 1 with the bore and passagewayshown in dotted lines;

FIG. 3 is a perspective view, partly broken away, showing the hubassembly mounted within a vortex tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 2 and 3, ahub assembly A in accordance with this invention includes a hub Icarrying vanes 2. Hub 1 and vanes 2 combine to define helical grooves 3.A longitudinal bore 4 is defined by hub 1. This bore 4 terminates at thedownstream or second end of hub 1 at opening 4a. Passageways 6a, 6bextend into vanes 2a, 2b from openings 7 in outermost surfaces 8. Thesepassageways 6a, 6b open tangentially into bore 4 at their inner ends.

FIG. 3 shows hub assembly A mounted in a vortex tube 9. When in place,the assembly A combines with the inner surface 1 l or vortex tube 9 todefine passages 10. As shown, each vane opening 7 registers with anopening 12 in the wall of vortex tube 9.

The hub 1 comprises two integral sections la, lb. Section 1b isessential to the invention, section In is optional.

Section 1b can be described as a solid cylinder which has fourlongitudinal, curved grooves 3 in its periphery. A circle B can be drawnto connect the outer edges of vanes 2. The diameter of circle B is theoutside diameter of the hub assembly A. This outside diameter isreferred to hereinbelow in describing some of the dimensions of theassembly.

Because it has a cylindrical form, section lb is adapted to fit snugglywithin vortex tube 9. Other hub configurations, such as a conical form,can be used; however the cylindrical shape is preferred.

Tailpipe section 1a is conical in form, tapering from about outsidediameter to near bore size. It functions to smooth the fiow dischargingfrom grooves 3 and diminishes turbulence.

Turning now to the hub assembly grooves 3, several factors need to beconsidered in selecting their number, size and shape. Firstly, thedirection of the flow into the vortex tube must be twisted enough by thegrooves to ensure a desirable degree of centrifugal separation therein.Secondly, it is usually necessary to keep the pressure drop across theseparator low. These two objectives are not compatible with each other.With a change in direction of flow, the gas velocity increases. Thisincrease in velocity is accompanied by a pressure drop. Therefore, thegreater the induced change in flow direction, the greater will be thepressure drop across the separator. Thirdly, it is preferable to use ahub which has a large cross' sectional area relative to the interiorcross sectional area of the vortex tube 9. By spreading the flow arounda large central hub, a central space 12 is ensured downstream from thehub into which the gas can converge. When the gas converges into thisspace 12, its rotational speed increases. This leads to a desired degreeof centrifugal separation. Finally, it is preferable to use four grooveswhich rotate through less then 90 i.e., the downstream ends of which lieat angles of less than 90 with respect to the upstream ends as measuredaround the periphery of the hub. This groove structure contributessubstantially to ease of manufacture by casting and is adapted togenerate the type of spin desired with a reasonably low pressure drop.

As a result of considerable experimentation, l have arrived at apreferred groove design which does the job and is easy to manufacture.More specifically, lv provide four curved grooves 3 of substantiallyequal cross-sectional area which rotate through an angle selected fromthe range 70 to 90, preferably 80, while curving such that theirupstream or first ends lie parallel to the hubs longitudinal axis whiletheir downstream or second ends lie at an angle of 30 to 50, preferably40, with respect to the said axis. The total cross-sectional area of thegrooves 3 is 0.3 to 0.6, preferably 0.5, times the area of circle B. Ifthe proportion is less than 0.3, the pressure drop will be too high formost uses. if the proportion is greater than 0.6, the apparatus becomesvery difficult to cast from steel due to, the thinness of the walls.

I combine these grooves 3 with a hub l which has a diameter at thedownstream or second end about 36 the interior diameter of vortex tube9.

The circular bore 4 extends longitudinally into hub I from thedownstream end opening 4a. It is centrally located so as to be co-axialwith the longitudinal axis of vortex tube 9. Its diameter is between 0.2and 0.5,

ref ab 0.3, tim the di eter f circle B. p I gi ovi d e two ta gential inets oi passageways 6a, 6b

which extend inwardly from openings 7 to communicate the upstream end ofbore 4. These passageways 6a, 6b are located substantially opposite toone another. They each have a cross-sectional area about A; thecross-sectional area of the bore 4 and are adapted to induce the recycleflow in the fore to follow a helical path having an angularity of about30.

I claim: 1. A hub assembly comprising: an elongate hub, having first andsecond ends, said hub carrying four outwardly protruding, longitudinallycurved vanes defining, in combination with the hub, four peripheral,curved grooves extending lengthwise along the hub, said grooves eachrotating through an angle of less than 90, one pair of oppositelydisposed vanes being thicker at their first ends than the other pair andsaid grooves being of substantially equal cross-sectional area; said hubdefining a centrally located, longitudinal bore which is open at thesecond end thereof and closed at the first end; each said thick vanedefining a passageway connecting the first end of the bore with anopening in the outermost surface of the vane. 2. The hub assembly as setforth in claim 1 wherein: the hub and vanes are cast to provide anintegral part. 3. The hub assembly as set forth in claim 2 wherein: thegrooves are curved such that their downstream ends lie at an angle of 30to 50 with respect to the hubs longitudinal axis. 4. The hub assembly asset forth in claim 2 wherein: the grooves rotate through an angleselected from the range to 5. The hub assembly as set forth in claim 4wherein: the sum of the cross-sectional areas of the grooves is between0.3 and 0.6 times the area of a circle having a diameter equal to theoutside diameter of the hub assembly. 6. The hub assembly as set forthin claim 5 wherein: the hub bore is cylindrical and its diameter isbetween 0.2 and 0.5 times the diameter of a circle having a diameterequal to the outside diameter of the hub assembly. In the disclosure: 7.The hub assembly as set forth in claim 6 wherein: the vane passagewayopens tangentially into the bore.

1. A hub assembly comprising: an elongate hub, having first and secondends, said hub carrying four outwardly protruding, longitudinally curvedvanes defining, in combination with the hub, four peripheral, curvedgrooves extending lengthwise along the hub, said grooves each rotatingthrough an angle of less than 90*, one pair of oppositely disposed vanesbeing thicker at their first ends than the other pair and said groovesbeing of substantially equal cross-sectional area; said hub defining acentrally locaTed, longitudinal bore which is open at the second endthereof and closed at the first end; each said thick vane defining apassageway connecting the first end of the bore with an opening in theoutermost surface of the vane.
 2. The hub assembly as set forth in claim1 wherein: the hub and vanes are cast to provide an integral part. 3.The hub assembly as set forth in claim 2 wherein: the grooves are curvedsuch that their downstream ends lie at an angle of 30* to 50* withrespect to the hub''s longitudinal axis.
 4. The hub assembly as setforth in claim 2 wherein: the grooves rotate through an angle selectedfrom the range 70* to 90*.
 5. The hub assembly as set forth in claim 4wherein: the sum of the cross-sectional areas of the grooves is between0.3 and 0.6 times the area of a circle having a diameter equal to theoutside diameter of the hub assembly.
 6. The hub assembly as set forthin claim 5 wherein: the hub bore is cylindrical and its diameter isbetween 0.2 and 0.5 times the diameter of a circle having a diameterequal to the outside diameter of the hub assembly. In the disclosure: 7.The hub assembly as set forth in claim 6 wherein: the vane passagewayopens tangentially into the bore.